GB160196A - Improvements in electric wave-form indicators or oscillographs - Google Patents

Abstract

160,196. Trichard, P. Sept. 5, 1919. Current meters.-The ordinate corresponding to any phase-angle of an alternating electromotive force E to be analysed is determined by the steady reading of a voltmeter V connected across a condenser A in a circuit including the plate P and filament F of a thermionic valve. Between the filament F and the grid G there is introduced an electromotive force D which is the sum of a constant pressure, from a source such as a battery B, and a sinusoidal alternating current C of an amplitude nearly equal to the pressure of the battery B. The pressure D is fairly high compared with the crest value cf the tension E to be analysed. Means are provided for varying the phase of the alternating current C with respect to that of the tension E to be analysed, the reading of the voltmeter V corresponding to each phase-angle being noted. The sinusoidal current C may be obtained from the tension E by the means shown. A resistance r, inductance l, and a pair of condensers c, c<1> are connected in series. and the condensers adjusted to resonance with the fundamental frequency. Alternatively, the harmonies of the tension E may be choked out by connecting a resistance and inductance in series across the tension E, another resistance and inductance in series across the resistance, and so on. The phase of the current C is varied by means of a rotating-field phase variometer H having coils of different impedance, the phaseangle being determined by the position of the movable coil. The phase variation may alternatively be effected by a resistance, a coil, and a condenser in known manner, cr by a small alternator, giving a sinusoidal wave, variably coupled with the alternator of which the wave form is to be determined.